例子讲解
/*
需求:对学生对象的年龄进行升序排序。
因为数据是以键值对形式存在的。
所以要使用可以排序的Map集合。TreeMap。
*/
import java.util.*;
class StuNameComparator implements Comparator<Student>//1、自定比较器StuNameComparator
{
public int compare(Student s1,Student s2)
{
int num = s1.getName().compareTo(s2.getName());
if(num==0)
return new Integer(s1.getAge()).compareTo(new Integer(s2.getAge()));
return num;
}
}
class MapTest2
{
public static void main(String[] args)
{
TreeMap<Student,String> tm =
new TreeMap<Student,String>(new StuNameComparator());//2、new 对象时传入自定义比较器StuNameComparator
tm.put(new Student("blisi3",23),"nanjing");
tm.put(new Student("lisi1",21),"beijing");
tm.put(new Student("alisi4",24),"wuhan");
tm.put(new Student("lisi1",21),"tianjin");
tm.put(new Student("lisi2",22),"shanghai");
//添加的元素就会按照比较器StuNameComparator的规定安排合适位置给它们了
Set<Map.Entry<Student,String>> entrySet = tm.entrySet();
Iterator<Map.Entry<Student,String>> it = entrySet.iterator();
while(it.hasNext())
{
Map.Entry<Student,String> me = it.next();
Student stu = me.getKey();
String addr = me.getValue();
System.out.println(stu+":::"+addr);
}
}
}
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